In cameras, what is called, digital cameras and the like, or a mobile information terminal such as a mobile phone into which camera functions are incorporated, in many cases, for convenience in mobile, reduction in dimensions, in particular, reduction in thickness are required. In order to realize a reduction in thickness when being transported, the respective intervals between a plurality of lenses are reduced by employing a telescopic expandable and contractible structure, by employing, what is called, a retracting type structure, a structure in order to reduce the dimension in a direction of the optical axis for photographing or picking up an image, is widely used.
Recently, as a solution to further reduce the thickness of the lens barrel when retracting, there is provided a structure in which at least a part of lens groups or retracting lens groups, except for an object side (subject side) end portion among the plurality of lens groups, is retracted out of the optical axis for photographing, and a space is ensured in order to retract the at least a part of the lens group positioned in an object side than the retracting lens group at a photographing extended state, what is called, a retracting type lens barrel is often used.
Patent Literature 1 discloses an example of retracting type barrel. Operation, in particular, an actuating operation disclosed in Patent Literature 1 will be described with reference to FIGS. 8 and 9. FIG. 8 schematically shows the operation of the retracting lens group when an actuation is initiated. FIG. 8(a) is a back view when viewed from an imaging surface, and FIG. 8(b) is a plan view when viewed from an upper surface.
Further, FIG. 9 schematically shows an operation of a photointerrupter in which a retracted lens group is positioned in a retracted position or not. FIG. 9(a) is a schematic view in which the retracting lens group is positioned in the retracted position, and FIG. 9(b) is a schematic view in which the retracting lens group is positioned out of the retracted position.
As shown in FIG. 8, the retracting lens group RG is positioned at the retracted position A in a retracted and stored state. The operation of the retracting lens group RG is as follows. In a photographing extended state, a front lens group which is positioned in an object side than the retracting lens group RG on the optical axis for photographing is drawn out, after a space into which the retracting lens group RG is inserted, is defined on the optical axis for photographing, the retracting lens group RG makes a revolution from a retracted position A to a position B on the optical axis and moves along an arcuate track after the retracting lens group RG reaches a position B on the optical axis, the retracting lens group RG moves straight in a direction of the object along the optical axis for photographing and thus reaches a position C on the optical axis for photographing.
Further, as shown in FIG. 9, a lens retaining frame RH of the retracting lens group RG is provided with a protruding portion RP for shielding, as shown in FIG. 9(a), when the retracting retaining frame RH of the retracting lens group RG is in the retracted position, the protruding portion for shielding RP is adapted to shield the photointerrupter PI.
The drive of the retracting lens group RG is executed from the retracted and collapsed state shown in FIG. 9(a) to a position on the optical axis for photographing shown in FIG. 9(b) and thus the photointerrupter PI is adapted to be in a permeable state by breaking the protruding portion for shielding RP away from the photointerrupter PI. In this case, an output signal of the photointerrupter PI is used as a reference positional signal and a position where the reference positional signal changes when the protruding portion for shielding RP is brought away from the photointerrupter PI, is adapted to be a reference position.
As shown in FIG. 8, while the retracting lens group RG makes a revolution from the retracted position A to a position B on the optical axis, if this lens barrel, for example, a camera into which this lens barrel is incorporated, is swung, or the lens barrel is subjected to a large vibration, the lens retaining frame RH of the retracting lens retaining frame RG being moved, returns toward a direction of the retracted position, or interferes with other parts and so on. As a result of this, an idle phenomenon of a driven control called “out of step” occurs and there happens that the retracting lens group is unable to correctly position on the optical axis.